At first, cancer, as a tiny mass of cells, causes no symptoms whatsoever (see also Overview of Cancer Overview of Cancer A cancer is an abnormal growth of cells (usually derived from a single abnormal cell). The cells have lost normal control mechanisms and thus are able to multiply continuously, invade nearby... read more ). As a cancer grows, its physical presence can affect nearby tissues (see also Warning Signs of Cancer Warning Signs of Cancer Cancer can cause many different symptoms, some subtle and some not at all subtle. (See also Overview of Cancer and Symptoms of Cancer.) Some symptoms develop early in the course of cancer, such... read more ). Also, some cancers secrete certain substances or trigger immune reactions that cause symptoms in other parts of the body that are not near to the cancer (paraneoplastic syndromes Paraneoplastic Syndromes Paraneoplastic (associated with cancer—see also Overview of Cancer) syndromes occur when a cancer causes unusual symptoms due to substances that circulate in the bloodstream. These substances... read more ).
Sometimes the initial indication is an abnormal result on a laboratory test done for another reason (for example, anemia Overview of Anemia Anemia is a condition in which the number of red blood cells is low. Red blood cells contain hemoglobin, a protein that enables them to carry oxygen from the lungs and deliver it to all parts... read more resulting from colon cancer found on a routine complete blood count).
Cancer affects nearby tissues by growing into or pushing on them, thus irritating or compressing them. Irritation typically causes pain. Compression may keep tissues from performing their normal functions. For example, a bladder cancer or a cancerous lymph node in the abdomen may compress the tube (ureter) connecting a kidney with the bladder, blocking the flow of urine. A lung cancer may block airflow through one segment of a lung, causing partial lung collapse and increasing the risk of infection.
When cancer grows in an area with a lot of space, such as in the wall of the large intestine or the lung cavity, it may not cause any symptoms until it becomes quite large. In contrast, a cancer growing in a more restricted space, such as on a vocal cord, may cause symptoms (such as hoarseness) when it is relatively small. If a cancer spreads (metastasizes) to other parts of the body, the same local effects of irritation and compression eventually occur, but in the new location, so the symptoms may be quite different.
Cancers that involve the membrane covering the lungs (pleura) or the baglike structure that surrounds the heart (pericardium) often ooze fluid, which collects around those organs. Large fluid collections can interfere with breathing or the pumping of the heart.
Many cancers are typically painless at first, although pain may be an early symptom of some cancers, such as brain tumors that cause headache and head and neck and esophageal cancers that cause painful swallowing. As cancers grow, the first symptom is often a mild discomfort, which may steadily worsen into increasingly severe pain as the cancer enlarges. The pain may result from the cancer compressing or eroding into nerves or other structures. However, not all cancers cause severe pain. Similarly, lack of pain does not guarantee that a cancer is not growing or spreading.
At first, a cancer may bleed slightly because its blood vessels are fragile. Later, as the cancer enlarges and invades surrounding tissues, it may grow into a nearby blood vessel, causing bleeding. The bleeding may be slight and undetectable or detectable only with testing. Such is often the case in early-stage colon cancer. Or, particularly with advanced cancer, the bleeding may be more significant, even massive and life threatening.
The site of the cancer determines the site of the bleeding. Cancer anywhere along the digestive tract can cause bleeding in the stool. Cancer anywhere along the urinary tract can cause bleeding in the urine. Other cancers can bleed into internal areas of the body. Bleeding into the lungs can cause the person to cough up blood.
Certain cancers produce substances that cause excess clot formation Excessive Clotting Excessive clotting (thrombophilia) occurs when the blood clots too easily or excessively. Inherited and acquired disorders can increase blood clotting. Clots cause legs or arms to swell. Blood... read more , mainly in the veins of the legs (deep vein thrombosis Deep Vein Thrombosis (DVT) Deep vein thrombosis is the formation of blood clots (thrombi) in the deep veins, usually in the legs. Blood clots may form in veins if the vein is injured, a disorder causes the blood to clot... read more ). Blood clots in leg veins sometime break off and travel to a lung (pulmonary embolism Pulmonary Embolism (PE) Pulmonary embolism is the blocking of an artery of the lung (pulmonary artery) by a collection of solid material brought through the bloodstream (embolus)—usually a blood clot (thrombus) or... read more ), which can be fatal. Excessive clotting is common in people with pancreatic, lung, and other solid tumors and in people with brain tumors.
Weight loss and fatigue
Commonly, a person with cancer experiences weight loss Involuntary Weight Loss Involuntary weight loss refers to weight loss that occurs when a person is not dieting or otherwise trying to lose weight. Because everyone's weight goes up and down slightly over time (such... read more and fatigue Fatigue Fatigue is when a person feels a strong need to rest and has so little energy that starting and sustaining activity is difficult. Fatigue is normal after physical exertion, prolonged stress... read more , which can worsen as the cancer progresses. Some people notice weight loss despite a good appetite. Others lose their appetite and may even become nauseated by food or have difficulty swallowing. They may become very thin. People with advanced cancer are often very tired. If anemia Overview of Anemia Anemia is a condition in which the number of red blood cells is low. Red blood cells contain hemoglobin, a protein that enables them to carry oxygen from the lungs and deliver it to all parts... read more develops, these people may find that they feel tired or become short of breath with even slight activity.
Swollen lymph nodes
As a cancer begins to spread around the body, it may first spread to nearby lymph nodes Overview of the Lymphatic System The lymphatic system is a vital part of the immune system. It includes organs such as the thymus, bone marrow, spleen, tonsils, appendix, and Peyer patches in the small intestine that produce... read more , which become swollen. The swollen lymph nodes are usually painless, and they may feel hard or rubbery. They may be freely moveable, or if the cancer is more advanced, they may become stuck to the surrounding tissues, or to each other.
Neurologic and muscular symptoms
Cancer can grow into or compress nerves or the spinal cord, causing any of several neurologic and muscular symptoms, including pain, weakness, or a change in sensation (such as tingling sensations). When a cancer grows in the brain, symptoms may be hard to pinpoint but can include confusion, dizziness, headaches, nausea, changes in vision, and seizures. Neurologic symptoms may also be part of a paraneoplastic syndrome Paraneoplastic Syndromes Paraneoplastic (associated with cancer—see also Overview of Cancer) syndromes occur when a cancer causes unusual symptoms due to substances that circulate in the bloodstream. These substances... read more .
Cancer can compress or block the airways in the lungs, causing shortness of breath, cough, or pneumonia. Shortness of breath can also occur when the cancer causes a large pleural effusion Pleural Effusion Pleural effusion is the abnormal accumulation of fluid in the pleural space (the area between the two layers of the thin membrane that covers the lungs). Fluid can accumulate in the pleural... read more , bleeding into the lungs, or anemia Overview of Anemia Anemia is a condition in which the number of red blood cells is low. Red blood cells contain hemoglobin, a protein that enables them to carry oxygen from the lungs and deliver it to all parts... read more .